This invention relates to a head positioner for use in an X-ray or ultra-short wave cephalotomograph, computer tomograph, dental pantomograph, temporomandibular joint radiograph, and the like.
Hitherto, X-ray cephalotomography has been practiced mainly in neurosurgical diagnoses, while in dental diagnoses such photography has not been in general practice. Today, however, needs for radiotomography are increasing in dental fields such as oral surgery, temporomandibular joints, implantation, and orthodontic treatment, and it is desired that accurate and quantitative information be obtained repetitively in same conditions by radiotomography and otherwise on matters such as buccolingual denture inclination and antagonistic tipping angle; sectional configuration of jaw bones and, more particularly, cortical-bone configuration, spongy-bone distribution, and kinematic position of inferior alveolar veins; and spacial position of impacted third molar.
In this conjunction, various improvements have been made with respect to tomographic apparatuses per se, and tomographs which can exhibit good performance accuracy have been proposed. However, insofar as head positioners for use in radiotomography, no such positioner has been proposed which can exhibit good practical performance accuracy.
In Japanese Utility Model Laid-Open Publication No. 61-34209, for example, there is described a technique for fixing the head of a subject in position by means of an anchor band. In Japanese Patent Laid-Open Publication Nos. 61-94639, 60-58127, and 61-203948, there are disclosed techniques such that a fixing member is applied to the ears, cranial fossa, or the like portion of the subject to fix the head in position. However, these techniques are designed to fix the head of the subject through the intermediary of a skin portion or the hair of the subject over which the fixing member is applied, and therefore no satisfactory positioning can be achieved because of the resiliency of the skin or other portions; furthermore, the head cannot be tightly bound by the anchor band or fixing member, which in fact also prevents the head from being completely fixed in position. As such, with these head positioners, the head of the subject cannot be repeatedly fixed in same conditions and it is virtually impossible to obtain laminograms of the subject under same conditions during the pre-treatment, in-treatment, and post-treatment stages.
Japanese Utility Model Laid-Open Publication No. 61-14006 discloses a head positioner which can solve these problems to some extent. This head positioner, as FIG. 7 shows, comprises a fixing device 4 having a spherical element 3 adapted to be inserted in the palate of a subject 2 laid down on a bed 1 and to be subjected to a bite by the subject 2, the fixing device 4 being pivotally supported by a supporting member 5 of an image intensifier or the bed 1, and a mechanism 6 for fixing the fixing device 4 to a desired rotation angle position. However, since this positioner is such that the spherical element 3 of the fixing device 4 is inserted in the palate of the subject 2 and subjected to a bite, the positional relation between the spherical element 3 and the palate of the subject 2 is unstable; and therefore the positioner cannot be put in use unless the subject 2 is laid down on the bed. Another problem is that because of such instability, the relative position of the subject 2 and the image intensifier 7 cannot be constantly defined, which in fact means poor duplicability. Furthermore, the insertion of the spherical element is a possible cause of pain to the subject 2, and the positioner cannot be employed for purposes of jaw bone photographing.